Mid-end and high-end earphones with functions of voice communication and music-playing (or music-playing only) are widely used, which not only brings convenience to voice communication, but also the enjoyment of high-quality music provided by music software. Thus, the earphones are demanded by the user which can not only achieve excellent voice communication, but also present various kinds of life-like and vivid audio effects. Non-closed-type earphones are focused by more and more manufacturers and customers, with its small size, good portability, good cost performance and adaptability to the main equipment. Due to the restraint of small size of the earphone, the size of the speaker used therewith is also limited to this. The diameter of the speaker unit is usually between 6 mm and 18 mm, and the low-frequency effect of the earphone is limited by the small size of the speaker, so the earphone manufactures are actively making efforts to improve the low-frequency performance of the earphone. However, most of the manufacturers still focus on improving the low-frequency response of the speaker and the progress that has been made is limited.